What MS for FHF 905?

[Lc130]

Hi All

I'm still a beginner trying to restore my grandfather's FHF 905.  J Borel here in the US lists two mainsprings on their website. Which is correct?

Thank you

Charlie

[watchweasol]

Hi one would assume that as its an automatic the 771 with the braking bridle is the correct one. See attached tech sheet.   Do not forget to use the braking grease on the barrel wall.

775_fhf905 (1).pdf

[Nucejoe]

Dr ranfft lists fhf905.

[nickelsilver]

Generale Ressorts lists the 2938-X for the 905, 908, 90-4 and 90-9. The 2936-X is the same but 40mm shorter.

[Lc130]

The 771 is out of stock at J Borel.  Nickelsilver's kind advise for the 2938 is also indicated by an ebay listing for a 2938 for a that movement.  I'll get the 2938 and hope I don't make a mess of it as I usually do with MS.

Thank you all

Charlie

[Klassiker]

Careful! There is a 2938 and a 2938-X. You need the X.

[HSL]

The 771/FF 90-4 is the factory number for this movement and the GS 2938-X is a replacement for the same.
If possible I usually just go with the factory numbered one.

[Lc130]

3 hours ago, HSL said:

The 771/FF 90-4 is the factory number for this movement and the GS 2938-X is a replacement for the same.
If possible I usually just go with the factory numbered one.

Well that explains why there are two listed at Borel.  I wondered about that. They are out of 771.  So, I've ordered the replacement.